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If these are not suitable, please contact our sales team, and they will happily discuss your options. They can advise about coatings regarding viewport applications and provide theoretical curves for your convenience.

Torr is able to provide theoretical “curves” (plotted graphs) to display the estimated transmission and reflection levels for each AR coating and optic.

Torr formulates their own recipes in-house for custom coatings. These recipes are produced using specialist software. Test pieces are coated and then tested for compliance using our UV-vis-IR and FTIR spectrophotometers.

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Figure 2: The graphic on the left shows how opposing troughs and peaks cancel each other. The graphic on the right shows how two reflected waves from a coated face can be made to interfere destructively in this way. Because R2 has travelled further before reflection, its phase (peak/trough position) is changed relative to R1 such that the troughs and peaks are opposed.

To determine the success of the AR coatings, the transmission and reflection rates are measured using our spectrophotometers. These fire beams of light moving sequentially from UV to IR at the coated optic. The detector then measures the coating’s transmission and reflectance across the specified range, in comparison to the theoretical curve.

Torr Scientific fused silica viewports are offered with a four‑layer W‑anti‑reflective (WAR, named for the shape of the reflectance curve) coating on both sides of the window optimised to customer‑specified laser wavelengths. In many cases, the coating reduces reflectance to below 1% per face, or 2% total, at the key wavelengths specified. Please advise the important wavelengths or wavelength range with your enquiry or order. Wavelength ranges between 240 nm and 1550 nm are offered as standard, although coatings for other wavelength ranges can be quoted on request.

A common example is when you see a rainbow. The light from the sun is diffracted and refracted by water droplets in the air, creating the colorful spectrum we see.

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AR coatings work by creating a stepping stone in the difference between the refractive index of the optic and the external world.

VAR uses two layers of coating and is a high-performance approach for a singular wavelength.Recognisable by the distinctive “V” shape it forms on reflectance curves.

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Torr Scientific offers fused silica viewports with an AR (anti‑reflective) coating on each face comprising a single quarterwave layer of MgF2 optimised for a customer‑specified wavelength range. Please advise the important wavelengths or wavelength range with your enquiry or order. Wavelength ranges between 190 nm and 1550 nm are offered as standard, although coatings for other wavelength ranges can be quoted on request.

This process helps to ensure that the optic and it’s coating are targeting the correct wavelengths and achieving optimal transmission levels.

BBAR (broadband) uses multiple layers to optimise for a continuous range of wavelengths.This high-performance coating works best when the lower range is no less than half the upper range (e.g., 500nm – 1000nm).

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There are a variety of different wavelengths that can be targeted with AR coatings, from deep ultraviolet (UV) all the way through to Infrared (IR). With the ability for a single wavelength, multiple, or a range of wavelengths to be targeted by altering the type of coating.

Additionally, there are a wide range of optical materials available for AR coatings, all of which have their own unique benefits.

Other optics options for coating include lead glass, barium fluoride, potassium fluoride, and magnesium fluoride. Find out more on the Torr Scientific Vacuum Viewports webpage.

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In complex cases where a greater number, or a larger range of wavelengths are required, a SPAR (special) coating is possible.Please contact the sales team for more information if this is a consideration for a project or purchase.

Torr Scientific offers a wide range of Anti-Reflective (AR) coatings to improve the efficiency of laser transmission and to minimise the reflections from optics within vacuum viewports.

Diffraction is used in many technologies such as CD players and diffractive lenses for glasses. Refraction is used in lenses for glasses and cameras, as well as in the design of optical instruments like microscopes and telescopes.

To coat the optics, they are placed within a vacuum chamber in which a high energy electron beam heats the coating material to over 1000°C. As the material is rapidly heated, it transforms into a vapour cloud, coating the optic.

Torr Scientific laser viewports are offered with a two‑layer V‑anti‑reflective (VAR, named for the shape of the reflectance curve) coating on both sides of the window optimised to a customer specified laser wavelength. The coating reduces reflectance to below 1% per face, or 2% total, at the wavelength specified. Please advise the laser wavelength with your enquiry or order. Wavelengths between 240 nm and 1550 nm are offered as standard, although coatings for other wavelengths can be quoted on request. Viewports with coatings for a wavelength range can also be offered.

Diffraction is the bending of waves around obstacles or through small openings, while refraction is the change in direction of a wave when it passes through a medium with different density.

Ar coating

AR coatings are typically manufactured for vacuum optics viewports, Torr offers a wide range of optic materials. A full list of coated and non-coated available optics can be found on the Torr Scientific Vacuum Viewports webpage.

Diffraction causes light to spread out and create patterns when it passes through small openings or around objects. Refraction causes light to bend when it moves from one medium to another, such as from air to water.

Torr Scientific fused silica viewports are offered with a four‑layer broadband anti‑reflective (BBAR) coating on both sides of the window optimised to a customer-specified laser wavelength range. In many cases, the coating reduces reflection to below 1% per face or 2% total at the key wavelengths specified. Please advise the important wavelengths or wavelength range with your enquiry or order. Wavelength ranges between 240 nm and 1550 nm are offered as standard, although coatings for other wavelength ranges can be quoted on request.

It can be complex to determine which AR coating is best for each project, it is a combination of factors surrounding the desired application and required wavelengths.

Theoretical reflectance curves for a single BBAR-coated face of fused silica. As the wavelength range increases the reflectance gets poorer.

Differences between the refractive indices of the air and the optic leads to reflections. These reflections occur on both the air‑side and the internal face of the optic. Applying an anti‑reflective coating to both faces creates destructive interference to reduce reflections.

WAR coating is optimal when two separate wavelengths are required at a high-performance transmission.Recognisable for the “W” shape the coating forms within reflectance curves.

Both diffraction and refraction have unique properties and are important in different ways. Neither is inherently better than the other, but they both play important roles in understanding and manipulating light in various applications.